Candida albicans and non-C. albicans Candida species are increasingly being isolated from patients in highrisk categories, most notably, those who have undergone stem cell transplantation (SCT). Identification of the presence of non-C. albicans Candida species early in the course of the transplant procedure is important, as these species exhibit different sensitivities to the available antifungal treatments and cause mortality at rates that vary from those for C. albicans. Amplified fragment length polymorphism (AFLP) analysis has been shown to be a reliable method of reproducibly identifying medically important Candida species. We investigated the use of serial AFLP analysis of 54 routine surveillance cultures for the identification and epidemiological examination of Candida sp. colonization in five consecutive children undergoing allogeneic SCT. One child became colonized with a C. albicans strain and remained colonized with this strain during the whole admission period. Another child had persistent colonization with a C. albicans strain with striking variations in its AFLP patterns over time, which was considered indicative of microevolution. Candida dubliniensis, Candida lusitaniae, and Saccharomyces cerevisiae were identified in the three remaining patients, with two children being simultaneously and transiently colonized with different species. These findings show that colonization with yeasts during transplantation is a complex and dynamic interaction between the host and the organism(s). In our study three strains from eight separate time points were incorrectly identified as C. albicans by a rapid enzyme test. AFLP analysis of surveillance cultures allowed more accurate and informative epidemiological evaluations of pathogenic yeasts in children during transplantation.

DNA analysis using pulsed‐field gel electrophoresis (PFGE) has emerged as one of the most sensitive epidemiological tools for the characterization of coagulase‐negative staphylococci (CNST). The significance of some minor differences observed between the DNA restriction pulsed patterns of two CNST strains are difficult to interpret since they can theoretically be due to minor chromosomal rearrangements or to phage DNA integration. The latter possibility was investigated by comparing DNA restriction patterns of Staphylococcus epidermidis strains with those of their lysogenized derivatives. In vitro lysogenisation was obtained by exposing the strains to phage 118II. The pulsed patterns of the lysogenized strains were compared to those of their parental strains, revealing a shift in size of approximately 50 kb in a single band which was shown by Southern blotting to contain prophage. One strain was lysogenized ten times, revealing a potential preferref attachment site for phage 118II. These results confirm that chromosomal integration of a phage can be responsible for minor stanle variations in DNA restriction patterns.

SUMMARYSixty-nine Staphylococcus aureas strains, 39 of which produced staphylococcal enterotoxin B (SEB + ) and 14 of which were associated with toxic shock (TS +), were studied using the following markers: serotyping, phage typing, antibiotyping, ribotyping, zymotyping and pulsed-field electrophoresis typing. Analysis of the results showed that the enterotoxin B producing strains were derived from at least three clones: the first two consisted of methicillin-susceptible strains, while the third included the methicillin-resistant (MRSA) strains. TS + strains of nongenital origin appeared to be distributed between the three clones, with no specific characters. INTRODUCTIONThe toxic shock syndrome toxin-i (TSST-1) of Staphylococcus aureus is responsible for staphylococcal toxic shock (TS). Most of the strains of genital origin and 50 % of others belong to the same clone [1]. Among the other S. aureus toxins, staphylococcal enterotoxin B (SEB) has been associated with disease recognized post-mortem [2,3]. Responsible mainly for food poisoning, it has also been associated with toxic shock [4][5][6]. The properties of SEB-producing strains (SEB+) are well documented; Asheshov and co-workers [7] demonstrated that the strains in the 94/96 phage complex were very often SEB+; Melconian and colleagues [8] observed that these strains were lysed mainly by phages of groups II and V; and Dornbusch and Hallander [9] have demonstrated a relationship between oxacillin resistance and toxin production. Recently, Lee and colleagues [10] have shown that TS-associated strains produced either TSST-1, enterotoxin B or, exceptionally, both; they have also shown that SEB+ strains belonged to the same zymotype, suggesting a clonal origin. The aim of the present study was to confirm or refute the existence of an enterotoxin-B producing cell clone by studying the phenotypic and genotypic characters of SEB + strains (whether or not associated with TS) as well as non-producing strains, using six different

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